The present invention relates to a servocontrol by ultrasonics of mechanical components in the relative master - slave position and radiology apparatus incorporating such a servocontrol. It is in particular used in radiology, where an operator brings a radiation source into a position at where it is a needed to align a detector of the X-ray image with the source.
The present invention is used in the servocontrol of the relative positions.
In the prior art, it is known to use ultrasonics for controlling displacements of mechanical components, which carry transducers and receive remote control commands by ultrasonics. The acquisition of data of the distance of the mechanical component dependent on a point of origin is brought about by echo reflection measurement. An echo transmitted by a transmitting probe is reflected onto the mechanical component and returns after a certain time, whose measurement indicates the absolute position found of the mechanical component. To obtain a satisfactory accuracy, such devices require a large amount of electronics. It is an advantage of the present invention that it considerably simplifies the control electronics and improves the relative precision of these servocontrols.
Distance measuring solutions using ultrasonic beams through the air have particularly been developed for the setting of focal lengths of photographic lenses. The remote control of household or domestic appliances such as television sets by ultrasonics through the air is well known. The application of such methods to metric servocontrol with an accuracy of better than 1 mm involves signal coding on several tens of bits, which considerably increases the weight and cost of the electronics. It is an advantage of the present invention that it makes it possible to considerably reduce the number of bits to be processed for high precision levels, even in the case of displacements of several meters.
The invention is particularly advantageous in that it can be adapted to solve various problems. More particularly, in radiology it is known that the alignment of two movable mechanical components is a difficult problem. This is the case with an X-ray source, which has to be accurately positioned on the reception optics of an X-ray film holder.
The present invention permits an alignment of these two components with a high degree of accuracy and without increasing the size of the electronic means.